When constructing low sensitive weapon systems, Insensitive Munitions, abbreviated IM, is an area to be considered and where to take care of the problems arising when the weapon system is subjected to heating. It is very important especially for personal safety reasons but also for transport classification reasons and for IM status reasons that a weapon system not can be brought into violent reactions when it is subjected to external stimuli.
A problem in connection to the above is that enclosed explosive materials subjected to heating will result in that the explosive materials are set to fire and burned. In this connection stronger enclosures result in more violent reactions.
An example of a cartridge case according to the first paragraph is previously known from FR 2 686 410 A1. The disclosed cartridge case comprises a shape memory material in the shape of a ring considerably elongated perpendicular to its radius located in a space between the base plate and the bottom section. Under normal temperature conditions the shape memory material is positioned in the space to lock the base plate to the bottom section of the cartridge case. In case of a temperature increase such that the temperature exceeds a predefined critical value, the shape memory material returns to a former shape positioning the shape memory material more inwards in the space resulting in that the base plate is unblocked. The arrangement of the shape memory material suffers from some problems. One problem is that the space between the base plate and the bottom section is voluminous to be able to house the considerably elongated shape memory material both in blocked and unblocked positions. This fact inter alia renders a distinct positioning of the shape memory material difficult in blocked and unblocked positions. There is also a risk that the movement of the shape memory material between blocked and unblocked positions is indistinct inter alia due to the elongated and cornered shape. Furthermore, when the content of the cartridge case is subjected to heating the content is likely to expand. This results in that there is a risk that the shape memory material is secured between the base plate and the bottom section before a critical temperature for unblocking has been reached. This may result in that the base plate not is released at all or that the releasing of the base plate is unacceptably delayed.